The selection of relatively simple but effective ways of protecting rock art from decay has been an elusive goal. Preventive barriers are imperative but they protect only from people and animals, not from the natural processes of integration. It is vital to study the rocks and the bonding of pigment to them. Silica skins which have formed naturally over quartzite on exposed surfaces protect many of the ochre paintings in Kakadu National Park (Australia) from decay. These silica skins are apparently effective because of their thinness, discontinuous form over the grains on the rock face, stability in the warm climatic environment and permeability to liquide and vapour. The author calls for research into silica skins.